As Duncan, Uwe, and I have told you already, this may get frustrating in the
long run as changes may break your bindings. Accessing a hidden API is doing
so against the wishes of the API designers / maintainers...

You do not need a chroot or second computer either. Just how r-base-core-ra
uses the normal --prefix argument to configure to install into a second,
non-overlapping file tree, you could use /usr/lib/ROcaml/ or some directory
other than /usr/lib/R + /usr/share/R which are taken by the R package for
Debian. R developers use the same --prefix trick to keep r-releases,
r-patched, r-devel, ... installed at the same time.

Anyway, good luck with the endeavour. Something useful may well come from it.